A fairer comparison would be emissions over the car's lifetime. The electric SUV would still almost certainly come out on top, but it's probably closer than the 100 vs 15 MPG would make it seem.
> Battery manufacturing life-cycle emissions debt is quickly paid off. An electric vehicle’s higher emissions during the manufacturing stage are paid off after only 2 years compared to driving an average conventional vehicle, a time frame that drops to about one and a half years if the car is charged using renewable energy. Approximately half of a battery’s emissions come from electricity used in the manufacturing process
From https://theicct.org/sites/default/files/publications/EV-life...
The important takeaway is that greener electricity grid will help both the emissions from manufacturing, as well as emissions from usage